Stent delivery apparatus and method

ABSTRACT

Apparatus and methods for stent delivery provide for dilatation at a treatment site as well as stent delivery, using the same stent delivery apparatus. Apparatus generally include a catheter having at least one expandable member, at least one stent positionable thereon, and a sheath disposed over the expandable member and the stent. Some embodiments include separate expandable members for dilatation of a lesion and for stent expansion, while other embodiments use the same expandable member for both. In some embodiments a stent includes multiple separable stent segments. In various embodiments, self-expanding stents may be used. Methods involve positioning a stent delivery device at a treatment site, expanding an expandable member to dilate at least a portion of a lesion at the treatment site, and expanding (or allowing to expand) a stent at the treatment site.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 10/794,405 filed Mar. 3, 2004 (Attorney Docket No. 021629-002400US),which is a continuation-in-part of U.S. patent application Ser. No.10/637,713, filed Aug. 8, 2003 (Attorney Docket No. 021629-000340US)(now U.S. Pat. No. 7,309,350) issued Dec. 18, 2007, which is acontinuation-in-part of U.S. patent application Ser. No. 10/412,714,filed Apr. 10, 2003 (Attorney Docket No. 021629-000330US) (now U.S. Pat.No. 7,137,993) issued Nov. 21, 2006, which is a continuation-in-part ofapplication Ser. No. 10/306,813, filed Nov. 27, 2002 (Attorney DocketNo. 021629-000320US), which is a non-provisional of U.S. ProvisionalPatent Application Ser. No.: 60/336,967, filed Dec. 3, 2001 (AttorneyDocket No. 021629-000300US), and 60/364,389, filed Mar. 13, 2002(Attorney Docket No. 021629-000310US). The entire disclosures of theabove-listed references are hereby fully incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates generally to medical devices and methods.More particularly, the invention relates to apparatus and methods forindependently delivering a plurality of luminal prostheses within a bodylumen.

Stenting has become an increasingly important treatment option forpatients with coronary artery disease. Stenting involves the placementof a tubular prosthesis within a diseased coronary artery to expand thearterial lumen and maintain the patency of the artery. Early stenttechnology suffered from problems with restenosis, the tendency of thecoronary artery to become re-occluded following stent placement. Inrecent years, however, improvements in stent design and the advent ofdrug-eluting stents have reduced restenosis rates dramatically. As aresult, the number of stenting procedures being performed in the UnitedStates, Europe, and elsewhere has soared.

Stents are delivered to the coronary arteries using long, flexiblevascular catheters, typically inserted through a femoral artery. Forself-expanding stents, the stent is simply released from the deliverycatheter, and it resiliently expands into engagement with the vesselwall. For balloon expandable stents, a balloon on the delivery catheteris expanded which expands and deforms the stent to the desired diameter,whereupon the balloon is deflated and removed.

Despite many recent advances in stent delivery technology, a number ofshortcomings still exist. For example, current stent delivery cathetersare not capable of customizing the length of the stent in situ to matchthe size of the lesion to be treated. While lesion size may be measuredprior to stenting using angiography or fluoroscopy, such measurementsmay be inexact. If a stent is introduced that is found to be ofinappropriate size, the delivery catheter and stent must be removed fromthe patient and replaced with a different device of correct size.Moreover, current stent delivery devices cannot treat multiple lesionswith a single catheter. If multiple lesions are to be treated, a newcatheter and stent must be introduced for each lesion to be treated.

Additionally, currently available stent delivery devices are notwell-adapted for treating vascular lesions that are very long and/or incurved regions of a vessel. Current stents have a discrete length thatis relatively short due to their stiffness. If such stents were madelonger, to treat longer lesions, they would not conform well to thecurvature of vessels or to the movement of vessels on the surface of thebeating heart. On the other hand, any attempt to place multiple stentsend-to-end in longer lesions is hampered by the inability to maintainappropriate inter-stent spacing and to prevent overlap of adjacentstents. Such shortcomings in the prior art are addressed by theinventions described in U.S. patent application Ser. No. 10/412,714(Attorney Docket No. 021629-000330US), which is hereby fullyincorporated by reference, and Ser. No. 10/637,713, which was previouslyincorporated by reference.

Even with improvements such as those described in the above-referencedpatent applications, further improvements in stent delivery devices andmethods are still being sought. For example, before a coronary stent isdeployed in a stenotic lesion, the physician will typically first dilatethe lesion with an angioplasty balloon. Following such “predilatation,”the angioplasty catheter is removed and a stent delivery catheter isadvanced to the treatment site to deploy the stent. One of thesignificant advantages of the stent delivery systems described in U.S.patent application Ser. Nos. 10/412,714 and 10/637,713, incorporatedabove, is the ability to treat multiple lesions at different locationswithout removing or replacing the catheter. Such a stent deliver systemmay be positioned at a first lesion for deployment of a first stent of adesired length, then moved to a second site where a second stent of adifferent length may be deployed. This may be repeated for multiplelesions without exchanging catheters, which saves time and eliminatesthe inefficiency of using multiple catheters. Such efficiencies arereduced, however, if it is necessary to use an angioplasty catheter topredilate lesions and a separate stent delivery catheter to deliverstents. If separate predilatation and stent delivery catheters are used,it may often be necessary to exchange, or “swap out,” the two cathetersmultiple times during a stenting procedure.

Therefore, it would be desirable to have stent delivery systems thatcould be used to predilatate lesions without requiring a separateangioplasty catheter. Ideally, such stent delivery systems would allowfor separate predilatation of multiple and/or long lesions as well asseparate stent deployment at those lesions, without requiring anycatheters to be exchanged. Preferably, such systems would also enable auser to adjust the length of the predilatation device to match thelength of the lesion to be treated. At least some of these objectiveswill be met by the present invention.

BRIEF SUMMARY OF THE INVENTION

The invention provides apparatus and methods for delivering one or morestents into a body lumen. In one aspect of the present invention, astent delivery device for delivering at least one stent to a treatmentsite includes a catheter shaft having a proximal end and a distal end,at least one stent positionable on the catheter shaft, a stentdeployment mechanism for deploying at least a portion of the stent atthe treatment site, and a dilatation member for dilating at least aportion of a lesion at the treatment site independently of deploying theat least one stent. The deployment mechanism generally allows the lengthof the deployed portion of the stent to be selected by a user. In someembodiments, the length of deployed stent may be selected in situ.Similarly, in some embodiments the length of the dilatation member to beexpanded to dilate the lesion may be selected in situ.

In some embodiments, the stent deployment mechanism includes a stentexpansion member coupled with the catheter shaft near the distal end andat least one axially movable sheath disposed over at least part of thestent expansion member and stent thereon. In some embodiments, the stentexpansion member may also act as the dilatation member. Alternatively,the dilatation member may coupled with the sheath. In other embodiments,the dilatation member may be coupled with an inner shaft slidablydisposed within the catheter shaft.

In some embodiments, the at least one stent comprises a plurality ofseparable stent segments. Optionally, the separable stent segments maybe axially movable relative to the catheter shaft and/or the stentexpansion member. Such embodiments may optionally further include apusher member for advancing the stent segments along the catheter shaftand/or stent expansion member. In some embodiments including a sheath,as mentioned above, the sheath may be configured to constrain expansionof a first portion of the stent expansion member and a first pluralityof the stent segments while allowing expansion of a second portion ofthe stent expansion member and a second plurality of the stent segments.Optionally, the sheath may further include at least one separationdevice for separating the first plurality of stent segments from thesecond plurality, thus allowing for expansion of a stent segment withoutinterfering with adjacent stent segments.

In some embodiments, the dilatation member and the stent expansionmember may be independently expandable. Such embodiments may optionallyfurther include at least one inflation lumen for expanding thedilatation member. For example, in some embodiments the inflation lumenmay comprise a tubular member disposed concentrically over a sheathcoupled with the dilatation member. In alternative embodiments, theinflation lumen may comprise a tubular member coupled with and extendingalong the outer surface of a sheath coupled with the dilatation member.In other embodiments, the inflation lumen may be disposed within thewall of a sheath coupled with the dilatation member.

In another aspect of the invention, a stent delivery device fordelivering at least one stent to a treatment site comprises: a cathetershaft having a proximal end and a distal end; an expandable membercoupled with the catheter shaft near the distal end; at least one stentslidably positionable on the expandable member; and at least one axiallymovable sheath disposed over at least part of the expandable member andstent thereon. Generally, the sheath is axially movable relative to thecatheter body to expose at least a portion of the expandable memberwithout exposing the stent, and the sheath is also movable to expose atleast a portion of the stent to allow it to expand.

In some embodiments, the stent is self-expanding. For example, in someembodiments, the stent comprises a plurality of separable,self-expanding stent segments. The stent (or one or more stent segments)may be advanced along the expandable member, in some embodiments, by apusher member. Optionally, the sheath may be configured to constrainexpansion of a first plurality of the stent segments while allowingexpansion of a second plurality of the stent segments. In someembodiments, the sheath further comprises at least one separation devicefor separating the first plurality of stent segments from the secondplurality, thus allowing for expansion of a stent segment withoutinterfering with adjacent stent segments. In various embodiments, thestent segments may comprise any suitable shape memory material or thelike. In one embodiment, for example, the stent segments comprise athermal shape memory material, and the expandable member is configuredto accept one or more heated or cooled fluids to change a temperature ofthe stent segments.

In another aspect of the invention, a stent delivery device for treatinga target site in a vessel includes: a catheter shaft having a proximalend and a distal end; a first stent carried on the catheter shaft andbeing deployable therefrom; a second stent carried on the catheter shaftand being deployable therefrom independently of the first stent; and adilatation member for dilating the target site independently ofdeploying the first and second stents.

In another aspect of the invention, a stent delivery device fordelivering at least one stent to a treatment site includes: a cathetershaft having a proximal end and a distal end; a stent expansion membercoupled with the catheter shaft near the distal end; at least one stentpositionable on the stent expansion member; at least one axially movablesheath disposed over at least part of the stent expansion member andstent thereon; and a dilatation member coupled with the sheath fordilating one or more lesions at the treatment site. Again, the stent maycomprise a plurality of separable stent segments, and the stent segmentsmay optionally be axially movable relative to the stent expansionmember. Such an embodiment may also include a pusher member foradvancing the stent segments. The sheath and expandable members may haveany of the features described above.

In another aspect of the present invention, a stent delivery device fordelivering at least one stent to a treatment site includes: a cathetershaft having a proximal end and a distal end; at least one stentpositionable on the catheter shaft; at least one axially movable sheathdisposed over the catheter shaft and stent; an inner shaft slidablydisposed within the catheter shaft; and a dilatation member coupled witha distal end of the inner shaft for dilating one or more lesions at thetreatment site. In some embodiments, the stent may comprise a pluralityof separable stent segments, and the stent segments may optionally beaxially movable relative to the stent expansion member. Such anembodiment may also include a pusher member for advancing the stentsegments. The sheath and expandable members may have any of the featuresdescribed above.

In some embodiments, the inner shaft comprises a tubular catheter shaft.Alternatively, the inner shaft may comprise a guidewire. In someembodiments, the inner shaft is slidable to expose at least part of thedilatation member out of the distal end of the catheter shaft, andwherein the inner shaft is slidable to retract the dilatation member toa position at least partially within the catheter shaft. In someembodiments, the dilatation member is expandable while only a portion isexposed out of the distal end of the catheter shaft. In someembodiments, the dilatation member is positionable relative to thecatheter shaft to adjust a length of the exposed portion of thedilatation member to dilate a desired length of the lesion at thetreatment site.

Optionally, separate inflation lumens may be included for expandingeither or both of the stent expansion and dilatation members. Where aseparate lumen is included for expanding the dilatation member, in someembodiments the inflation lumen comprises a tubular member disposedconcentrically over the inner shaft. Alternatively, the inflation lumenmay comprise a tubular member disposed within the inner shaft. In otherembodiments, the inflation lumen may be disposed within the wall of theinner shaft.

In yet another aspect of the present invention, a method for deliveringat least one stent to a treatment site involves: positioning a distalportion of a stent delivery catheter device at the treatment site, thestent delivery catheter carrying at least one stent; expanding at leasta portion of an expandable member on the catheter device to dilate atleast a portion of a lesion at the treatment site; selecting adeployable portion of the stent having a selected length; and expandingthe deployable portion of the stent at the treatment site, andundeployed portion of the stent remaining in the delivery catheter. Someembodiments may optionally further involve positioning the deployableportion of the stent over the expandable member. In some embodiments,expanding the deployable portion of the stent comprises expanding theexpandable member. In some embodiments, the at least one stent comprisesa plurality of stent segments, and retracting the sheath exposes atleast one of the stent segments to self-expand at the treatment site.Such embodiments may optionally further include, after retracting thesheath: positioning the expandable member within the at least oneself-expanded stent segment; and expanding at least a portion of theexpandable member to further expand the stent segment.

In some embodiments, the method may also involve exposing the portion ofthe expandable member outside the sheath before the expanding step. Themethod may optionally further include retracting the portion of theexpandable member to a position within the sheath after the expandingstep. Some embodiments may also involve passing a fluid through theexpandable member while the stent segments are disposed thereon, whereinthe stent segments comprise a thermal shape memory material, and whereinpassing the fluid changes the temperature of the stent segments. Forexample, in some embodiments the passed fluid is heated to a temperaturehigher than body temperature, while in others it is cooled to atemperature lower than body temperature. In some embodiments, theportion of the expandable member is expanded using fluid.

In another aspect of the invention, a method for delivering at least onestent to a treatment site includes: positioning a distal portion of astent delivery catheter device at the treatment site, the stent deliverycatheter carrying at least one stent; expanding at least a portion of adilatation member of the catheter device to dilate at least a portion ofa lesion at the treatment site; and expanding at least a portion of astent expansion member of the catheter device to deploy at least aportion of the at least one stent at the treatment site. The method mayoptionally further include selecting a deployable portion of the stent,wherein the deployable portion is expanded by the stent expansion memberwhile an undeployed portion of the stent remains unexpanded in the stentdelivery catheter. Again, in some embodiments the at least one stentcomprises a plurality of stent segments, and deploying at least theportion comprises deploying at least one of the stent segments.

In some embodiments, the dilatation member is disposed on an outersurface of a sheath slidably disposed over the stent and the stentexpansion member. In such embodiments, the method may also includeretracting the sheath to expose at least the portion of the stentexpansion member and at least one stent. Alternative embodiments mayfurther involve sliding an inner shaft of the catheter device distallyrelative to the stent expansion member to expose at least the portion ofthe dilatation member, the dilatation member being disposed on the innershaft. In some embodiments, such a method may also include sliding thecatheter body distally over the inner shaft to position the stentexpansion member at the treatment site. Optionally, the dilatationmember may then be re-expanded at the treatment site after the stent isdeployed.

Further aspects of the nature and advantages of the invention willbecome apparent from the detailed description below taken in conjunctionwith the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a stent delivery catheter according tothe invention with sheath retracted and expandable member inflated.

FIG. 2A is a side cross-section of a distal portion of the stentdelivery catheter of FIG. 1 with expandable member deflated and sheathadvanced distally.

FIG. 2B is a side cross-section of a distal portion of the stentdelivery catheter of FIG. 1 with expandable member inflated and sheathretracted.

FIG. 3 is a transverse cross-section through line 3-3 of FIG. 2A.

FIG. 4 is a transverse cross-section through line 4-4 of FIG. 2A.

FIG. 5A is a side view of a first embodiment of a stent segmentaccording to the invention in an unexpanded configuration.

FIG. 5B is a side view of the stent segment of FIG. 5A in an expandedconfiguration.

FIG. 6A is a side view of a second embodiment of a stent segmentaccording to the invention in an unexpanded configuration.

FIG. 6B is a side view of two of the stent segments of FIG. 6A in anexpanded configuration.

FIGS. 7A-7E are side cut-away views of the stent delivery catheter ofthe invention positioned in a vessel with the stent segments of FIGS.5A-5B, illustrating various steps of delivering a prosthesis accordingto the method of the invention.

FIG. 8 is a side cut-away view of the stent delivery catheter of theinvention positioned in a vessel with the stent segments of FIGS. 6A-6Bin a deployed configuration.

FIG. 9 is a side cut-away view of a stent delivery catheter having anexpandable member disposed on a sheath according to one embodiment ofthe invention.

FIG. 10 is a side cut-away view of a stent delivery catheter having anexpandable member disposed on a slidable inner shaft according to oneembodiment of the invention.

FIGS. 11A and 11B are side cut-away views of a stent delivery catheterbeing used to dilate a lesion and place stent segments in the lesionaccording to one embodiment of the invention.

FIGS. 12A-12E are side views of a stent delivery catheter being used ina vessel to dilate a lesion and place stent segments in the lesionaccording to one embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

One embodiment of a stent delivery catheter according to presentinvention is illustrated in FIG. 1. Stent delivery catheter 20 includesa catheter body 22 comprising an outer sheath 25 slidably disposed overan inner shaft 27. An expandable member 24, preferably an inflatableballoon (shown in an inflated configuration), is mounted to inner shaft27 and is exposed by retracting sheath 25 relative to inner shaft 27. Atapered nosecone 28, composed of a soft elastomeric material to reducetrauma to the vessel during advancement of the device, is mounteddistally of expandable member 38. A stent 30, which preferably comprisesa plurality of separate or separable stent segments 32, is disposed onexpandable member 24 for expansion therewith. A guidewire tube 34 isslidably positioned through a guidewire tube exit port 35 in sheath 25proximal to expandable member 24. A guidewire 36 is positioned slidablythrough guidewire tube 34, expandable member 24, and nosecone 28 andextends distally thereof.

A handle 38 is mounted to a proximal end 23 of sheath 25 and includes anactuator 40 slidably mounted thereto for purposes described below. Anadaptor 42 is mounted to the proximal end of handle 38 and provides acatheter port 44 through which inner shaft 27 is slidably positioned. Aflush port 48 is mounted to the side of adaptor 42 through which a fluidsuch as saline can be introduced into the interior of catheter body 22.An annular seal (not shown) in catheter port 44 seals around inner shaft27 to prevent fluid from leaking through catheter port 44. Optionally, aclamp (not shown) such as a threaded collar, can be mounted to catheterport 44 to lock inner shaft 27 relative to handle 38.

Inner shaft 27 has a proximal end 50 to which is mounted an inflationadaptor 52. Inflation adaptor 52 is configured to be fluidly coupled toan inflation device 54, which may be any commercially available ballooninflation device such as those sold under the trade name “Indeflator™,”available from Advanced Cardiovascular Systems of Santa Clara, Calif.Inflation adaptor 52 is in fluid communication with expandable member 24via an inflation lumen (described below) in inner shaft 27 to enableinflation of expandable member 24.

Referring now to FIGS. 2A-2B, 3 and 4, which show a distal portion ofthe stent delivery catheter in cross-section, it may be seen that sheath25 may be extended up to nosecone 28 to fully surround expandable member24 and stent segments 32. One or more radiopaque markers 56 are mountednear a distal end 57 of sheath 25 to facilitate visualization of theposition of sheath 25 using fluoroscopy. In a preferred embodiment, twoannular markers 56 are spaced apart a length equal to the length of oneof stent segments 32 for purposes described more fully below. Sheath 25further includes a valve member 58 preferably spaced proximally fromdistal end 57 a distance equal to the length of one of stent segments32. Valve member 58 has an inwardly extending flange 60 configured tofrictionally engage stent segments 32 and thereby restrict the slidingmovement of stent segments 32 distally relative to sheath 25. Flange 60may be a polymeric material integrally formed with sheath 25 or aseparate annular member bonded or otherwise mounted to sheath 25.Various embodiments of valve member 58 are described in copendingapplication Ser. No. 10/412,714, Filed Apr. 10, 2003 (Attorney DocketNo. 021629-000330US), which is incorporated herein by reference.

Sheath 25 has a distal extremity 62 configured to surround expandablemember 24 and stent segments 32 disposed thereon when in an unexpandedconfiguration. Distal extremity 62 extends proximally to a junction 63,preferably aligned with the location of guidewire tube exit port 35,where distal extremity 62 is joined to a proximal extremity 64 thatextends proximally to handle 38 (see FIG. 1). In a preferred embodiment,distal extremity 62 has a length of about 15-35 cm and proximalextremity 64 as a length of about 100-125 cm. Proximal extremity 64 maybe constructed of a variety of biocompatible polymers or metals,preferably being stainless steel or Nitinol. Distal extremity 62 may bea polymer such as PTFE, FEP, polyimide, or Pebax, and is preferablyreinforced with a metallic or polymeric braid to resist radial expansionwhen expandable member 24 is expanded.

Preferably, proximal extremity 64 has a smaller transverse dimensionthan distal extremity 62 to accommodate the added width of guidewiretube 34 within the vessel lumen, as well as to maximize flexibility andminimize profile. In one embodiment, shown in FIG. 3, distal extremity62 is a tubular member having a first outer diameter, preferably about1.0-1.5 mm, and proximal extremity 64 is a tubular member having asecond, smaller outer diameter, preferably about 0.7-1.0 mm. At thejunction of proximal extremity 64 with distal extremity 62, aproximally-facing crescent-shaped opening 65 is formed between the twotubular members that creates guidewire tube exit port 35. Excess spacewithin crescent-shaped opening 65 may be filled with a filler materialsuch as adhesive.

In an alternative embodiment (not shown), a hole is formed in thesidewall of distal extremity 62 or proximal extremity 64 to createguidewire tube exit port 35. Proximally of guidewire tube exit port 35,the wall of sheath 25 adjacent to guidewire tube 34 is flattened orcollapsible inwardly thereby reducing the transverse dimension of sheath25 to accommodate the width of guidewire tube 34.

Guidewire tube 34 is slidably positioned through guidewire tube exitport 35. Preferably, guidewire tube exit port 35 is configured toprovide a total or partial fluid seal around the periphery of guidewiretube 34 to limit blood flow into the interior of sheath 25 and to limitleakage of saline (or other flushing fluid) out of sheath 25. This maybe accomplished by sizing guidewire tube exit port 35 appropriately soas to form a fairly tight frictional seal around guidewire tube 34 whilestill allowing the sliding motion thereof relative to sheath 25.Alternatively an annular sealing ring may be mounted in guidewire tubeexit port 35 to provide the desired seal.

Guidewire tube exit port 35 will be positioned to provide optimaltracking of stent delivery catheter 20 through the vasculature andmaximizing the ease with which the catheter can be inserted onto andremoved from a guidewire to facilitate catheter exchanges. Usually,guidewire tube exit port 35 will be positioned at a location proximal toexpandable member 24 when sheath 25 is extended fully distally up tonosecone 28, but a distance of no more than one-half the length ofsheath 25 from distal end 57. In preferred embodiments for coronaryapplications, guidewire tube exit port 35 is spaced proximally adistance of about 20-35 cm from the distal end 57 of sheath 25.

Guidewire tube 34 should extend proximally from guidewire tube exit port35 a distance at least as long as the longest possible stent that may bedeployed, e.g. 30-60 mm, to allow for retraction of sheath 25 thatdistance while retaining a portion of guidewire tube 34 external tosheath 25. Preferably guidewire tube 34 extends proximally a distance ofabout 3-15 cm from guidewire tube exit port 35 when sheath 25 is in afully distal position, with the proximal end thereof disposed a distanceof about 23-50 cm from the distal tip of nosecone 28. Where stentdelivery catheter 20 is to be positioned through a guiding catheter, theproximal end of guidewire tube 34 will preferably be positioned so as tobe within the guiding catheter when expandable member 24 is positionedat the target site for stent deployment. Guidewire tube 34 is preferablya highly flexible polymer such as PTFE, FEP, polyimide, or Pebax, andmay optionally have a metal or polymer braid embedded in it to increasekink-resistance.

Inner shaft 27 forms an inflation lumen 66 that is in communication withinterior of expandable member 24. In the distal extremity of stentdelivery catheter 20 inner shaft 27 is preferably formed of a polymersuch as PTFE, FEP, polyimide, or Pebax, and may be reinforced with ametallic braid for added radial strength and kink resistance. In theproximal extremity of delivery catheter 20, inner shaft 27 may be asimilar polymer or a metal such as stainless steel or Nitinol.

Expandable member 24 has an expandable balloon member 70 that is joinedto a non-expandable tubular leg 72. Expandable balloon member 70 is asemi-compliant polymer such as Pebax or Nylon. Tubular leg 72 ispreferably a polymer such as polyimide, PTFE, FEP or Pebax and mayoptionally be reinforced with a metal or polymer braid. Tubular leg 72has an open proximal end 74 through which guidewire tube 34 extends.Proximal end 74 of tubular leg 72 is fixed to distal end 68 of innershaft 27 and to guidewire tube 34, forming a fluid-tight seal. Balloonmember 70 has a distal end 76 bonded to an annular stop 78, which ismounted to nosecone 28. Stop 78 has a size and shape selected to engagestent segment 32 and provide a stop against which stent segments 32 canbe located in the ideal deployment position without being pushed beyondthe distal end of balloon member 70. Guidewire tube 34 passes throughthe interior of balloon member 70 and is mounted to nosecone 28, therebyproviding a passage through the distal portion of catheter body 22through which guidewire 36 may pass.

Optionally, within the interior of balloon member 70 an annular basemember 80 is mounted to guidewire tube 34 and has a diameter selected tourge balloon member 70 against stent segments 32 in their unexpandedconfiguration, thereby providing frictional engagement with stentsegments 32. This helps to limit unintended sliding movement of stentsegments 32 on balloon member 70. Base member 80 may be made of a softelastomer, foam, or other compressible material. Adjacent to the distaland proximal ends of base member 80 two annular radiopaque markers 82are mounted to guidewire tube 34, facilitating visualization of thelocation of balloon member 70 with fluoroscopy and enabling appropriatepositioning of stent segments 32 on balloon member 70. Alternatively,only a single marker 82 at the distal end of base member 80 may be used,or markers may be placed at other locations on nosecone 28, guidewiretube 34, or inner shaft 27. Such markers may be made of variousradiopaque materials such as platinum/iridium, tantalum, and othermaterials.

Stent segments 32 are slidably positioned over balloon member 70.Depending upon the number of stent segments 32 loaded in stent deliverycatheter 20, stent segments 32 may be positioned over both balloonmember 70 and tubular leg 72. In an exemplary embodiment, each stentsegment is about 2-8 mm in length, and up to 10-50 stent segments may bepositioned end-to-end in a line over balloon member 70 and tubular leg72. Stent segments 32 preferably are in direct contact with each other,but alternatively separate spacing elements may be disposed betweenadjacent stent segments, the spacing elements being movable with thestent segments along balloon member 70. Such spacing elements may beplastically deformable or self-expanding so as to be deployable withstent segments 32 into the vessel, but alternatively could be configuredto remain on balloon member 70 following stent deployment; for example,such spacing elements could comprise elastic rings which elasticallyexpand with balloon member 70 and resiliently return to their unexpandedshape when balloon member 70 is deflated. The spacing elements could bepushed to the distal end of balloon member 70 against stop 78 asadditional stent segments 32 are advanced distally.

Stent segments 32 are preferably a malleable metal so as to beplastically deformable by expandable member 24 as they are expanded tothe desired diameter in the vessel. Alternatively, stent segments 32 maybe formed of an elastic or super elastic shape memory material such asNitinol so as to self-expand upon release into the vessel by retractionof sheath 25. Stent segments 32 may also be composed of polymers orother suitable biocompatible materials. In self-expanding embodiments,expandable member 24 may also be used for predilatation of a lesionprior to stent deployment and/or for augmenting the expansion of theself-expanding stent segments, as is described in greater detail below.In some embodiments, stent segments 32 may be formed of a thermal shapememory material, and expandable member 24 may be used for accepting aheated or cooled fluid while in contact with stent segments 32 so as tochange the temperature of the stent segments 32, causing them to expandupon release. In some embodiments, expandable member 24, when containingcooled fluid, may be further used to help expand a lesion after stentsegments 32 are in place.

In preferred embodiments, stent segments 32 are coated with a drug thatinhibits restenosis, such as Rapamycin, Paclitaxel, analogs, prodrugs,or derivatives of the foregoing, or other suitable agent, preferablycarried in a bioerodible polymeric carrier. Alternatively, stentsegments 32 may be coated with other types of drugs and therapeuticmaterials such as antibiotics, thrombolytics, anti-thrombotics,anti-inflammatories, cytotoxic agents, anti-proliferative agents,vasodilators, gene therapy agents, radioactive agents,immunosuppressants, and chemotherapeutics. Such materials may be coatedover all or a portion of the surface of stent segments 32, or stentsegments 32 may include apertures, holes, channels, or other features inwhich such materials may be deposited.

Stent segments 32 may have a variety of configurations, including thosedescribed in copending application Ser. No. 60/440,839, filed Jan. 17,2003 (Attorney Docket No. 021629-000500US), which is incorporated hereinby reference. Other preferred stent configurations are described below.Stent segments 32 are preferably completely separate from one anotherwithout any interconnections, but alternatively may have couplingsbetween two or more adjacent segments which permit flexion between thesegments. As a further alternative, one or more adjacent stent segmentsmay be connected by separable or frangible couplings that are separatedprior to or upon deployment, as described in copending application Ser.No. 10/306,813, filed Nov. 27, 2002 (Attorney Docket No.021629-000320US), which is incorporated herein by reference.

A pusher tube 86 is slidably disposed over inner shaft 27 and has adistal extension 88 coupled to a pusher ring 90. Pusher ring 90 isslidable over tubular leg 72 and engages the stent segment 32 at theproximal end of the line of stent segments 32. At its proximal end (notshown), pusher tube 86 is coupled to sliding actuator 40 on handle 38(see FIG. 1). In this way, pusher tube 86 can be advanced distallyrelative to inner shaft 27 to urge stent segments 32 distally overexpandable member 24 (or pusher tube 86 may be held in position whileretracting expandable member 24 relative to stent segments 32) until thestent segments engage stop 78. In addition, pusher tube 86 can be usedto hold stent segments 32 in place on expandable member 24 while sheath25 is retracted to expose a desired number of stent segments 32, asshown in FIG. 2B. Pusher tube 86 may be constructed of a variety ofbiocompatible polymers or metals, preferably being stainless steel orNitinol. Distal extension 88 and pusher ring 90 may be a polymer such asPTFE, FEP, polyimide, or Pebax, and are preferably reinforced with ametallic or polymeric braid to resist radial expansion when expandablemember 24 is expanded.

It can be seen that with sheath 25 retracted a desired distance,expandable member 24 is allowed to expand when inflation fluid isdelivered through inflation lumen 66, thereby expanding a desired numberof stent segments 32 exposed distally of sheath 25. The remainingportion of expandable member 24 and the remaining stent segments 32within sheath 25 are constrained from expansion by sheath 25.

FIG. 2B further illustrates that when sheath 25 is retracted relative toexpandable member 24, guidewire tube exit port 35 becomes further awayfrom the point at which guidewire 36 exits the proximal end 74 oftubular leg 72, increasing the distance that guidewire 36 must passwithin the interior of sheath 25. Advantageously, guidewire tube 34provides a smooth and continuous passage from the tubular leg 72 throughguidewire tube exit port 35, eliminating any problems that might resultfrom changing the alignment of the two. This is particularly importantin the present invention where the stent delivery catheter may carry alarge number of stent segments 32 and sheath 25 may be retracted asubstantial distance relative to expandable member 24, resulting insubstantial misalignment of guidewire tube exit port 35 relative totubular leg 72.

In order to confirm the positioning of stent segments 32 on expandablemember 24, fluoroscopy is used to visualize stent segments 32 relativeto markers 82 on inner shaft 27. In addition, by fluoroscopicvisualization of markers 56 on sheath 25 the user can see the extent ofretraction of sheath 25 relative to expandable member 24 and view thelocation of the exposed stent segments 32 relative to sheath 25.Visualization of stent segments 32 is further enhanced with the use ofradiopaque markers and/or materials in or on the stent segmentsthemselves. Markers of radiopaque materials may be applied to theexterior of stent segments 32, e.g., by applying a metal such as gold,platinum, a radiopaque polymer, or other suitable coating or mark on allor a portion of the stent segments. Alternatively, stent segments 32 mayinclude a radiopaque cladding or coating or may be composed ofradiopaque materials such as L-605 cobalt chromium (ASTM F90), othersuitable alloys containing radiopaque elements, or multilayeredmaterials having radiopaque layers. In yet another alternative, stentsegments 32 may have a geometry conducive to fluoroscopic visualization,such as having struts of greater thickness, sections of higher density,or overlapping struts. Some of the possible materials that may be usedin stent segments 32 include (by ASTM number):

-   F67-00 Unalloyed Titanium-   F75-01 Cobalt-28 Chromium-6 Molybdenum Alloy-   F90-01 Wrought Cobalt-20 Chromium-15 Tungsten-10 Nickel Alloy-   F136-02a Wrought Titanium-6 Aluminum-4 Vanadium ELI Alloy-   F138-00, F139-00 Wrought 18 Chromium-14 Nickel-2.5 Molybdenum    Stainless Steel Bar or Sheet-   F560-98 Unalloyed Tantalum-   F562-02 Wrought 35 Cobalt-35 Nickel-20 Chromium-10 Molybdenum Alloy-   F563-00 Wrought Cobalt-20 Nickel-20 Chromium 3.5 Molybdenum-3.5    Tungsten-5 Iron Alloy-   F688 Wrought Cobalt-35 Nickel-20 Chromium-10 Molybdenum Alloy-   F745-00 18 Chromium-12.5 Nickel-2.5 Molybdenum Stainless Steel-   F799-02 Cobalt-28 Chromium-6 Molybdenum Alloy-   F961-96 Cobalt-35 Nickel-20 Chromium-10 Molybdenum Alloy-   F1058-02 Wrought 40 Cobalt-20 Chromium-16 Iron-15 Nickel-7    Molybdenum Alloy-   F1091-02 Wrought Cobalt-20 Chromium-15 Tungsten-10 Nickel Alloy-   F1108 Titanium-6 Aluminum-4 Vanadium Alloy-   F1295-01 Wrought Titanium-6 Aluminum-7 Niobium Alloy-   F1314-01 Wrought Nitrogen-strengthened 22 Chromium-13 Nickel-5    Manganese-2.5 Molybdenum Stainless Steel Alloy-   F1241-99 Unalloyed Titanium Wire-   F1350-02 Wrought 18 Chromium-14 Nickel-2.5 Molybdenum Stainless    Steel Wire-   F1377-98a Cobalt-28 Chromium-6 Molybdenum Powder coating-   F1472-02a Wrought Titanium-6 Aluminum-4 Vanadium Alloy-   F1537-00 Wrought Cobalt-28 Chromium-6 Molybdenum Alloy-   F1580-01 Titanium and Titanium-6 Aluminum-4 Vanadium Alloy Powder    coating-   F1586-02 Wrought Nitrogen Strengthened 21 Chromium-10 Nickel-3    Manganese-2.5 Molybdenum Stainless Steel Bar-   F1713-96 Wrought Titanium-13 Niobium-13 Zirconium Alloy-   F1813-01 Wrought Titanium-12 Molybdenum-6 Zirconium-2 Iron Alloy-   F2063-00 Wrought Nickel-Titanium Shape Memory Alloys-   F2066-01 Wrought Titanium-15 Molybdenum Alloy-   F2146-01 Wrought Titanium-3 Aluminum-2.5 Vanadium Alloy Seamless    Tubing-   F2181-02a Wrought Stainless Steel Tubing

A first preferred geometry of stent segments 32 is illustrated in FIGS.5A-5B. FIG. 5A illustrates a portion of a stent segment 32 in anunexpanded configuration, shown in a planar shape for clarity. Stentsegment 32 comprises two parallel rows 98A, 98B of I-shaped cells 100formed around an axis A so that stent segment 32 has a cylindricalshape. Each cell 100 has upper and lower axial slots 102 aligned withthe axial direction and a circumferential slot 104. Upper and lowerslots 102 preferably have an oval, racetrack, rectangular or otheroblong shape with a long dimension L generally parallel to axis A and ashort dimension W perpendicular thereto. Axial slots 102 are bounded byupper axial struts 106 and lower axial struts 107, curved outer ends 108and curved inner ends 110. Each circumferential slot 104 is bounded byan outer circumferential strut 109 and an inner circumferential strut111. Each I-shaped cell 100 is connected to the adjacent I-shaped cell100 in the same row 98A or 98B by a circumferential connecting strut113. All or a portion of cells 100 in row 98A merge or join with cells100 in row 98B at the inner ends 110, which are integrally formed withthe inner ends 110 of the adjacent cells 100.

In a preferred embodiment, a spacing member 112 extends outwardly in theaxial direction from a selected number of outer circumferential struts109 and/or connecting struts 113. Spacing member 112 preferably itselfforms a subcell 114 in its interior, but alternatively may be solidwithout any cell or opening therein. For those spacing members 112attached to outer circumferential struts 109, subcell 114 preferablycommunicates with I-shaped cell 100. Spacing members 112 are configuredto engage the curved outer ends 108 of an adjacent stent segment 32 soas to maintain appropriate spacing between adjacent stent segments. Inone embodiment, spacing members 112 have outer ends 116 with twospaced-apart protrusions 118 that provide a cradle-like structure toindex and stabilize the curved outer end 108 of the adjacent stentsegment. Preferably, spacing members 112 have an axial length of atleast about 10%, more preferably at least about 25%, of the longdimension L of I-shaped cells 100, so that the I-shaped cells 100 ofadjacent stent segments are spaced apart at least that distance. Becausespacing members 112 experience little or no axial shortening duringexpansion of stent segments 32, this minimum spacing between stentsegments is maintained both in the unexpanded and expandedconfigurations.

FIG. 5B shows stent segment 32 of FIG. 5A in an expanded configuration.It may be seen that cells 100 are expanded so that upper and lower slots102 are diamond shaped with circumferential slots 104 remainingbasically unchanged. This results in some axial shortening of the stentsegment, thereby increasing the spacing between adjacent stent segments.The stent geometry is optimized by balancing the amount of axialshortening and associated inter-segment spacing, the desired degree ofvessel wall coverage, the desired metal density, and other factors.Because the stent is comprised of multiple unconnected stent segments32, any desired number from 2 up to 10 or more stent segments may bedeployed simultaneously to treat lesions of any length. Further, becausesuch segments are unconnected to each other, the deployed stentstructure is highly flexible and capable of deployment in long lesionshaving curves and other complex shapes.

As an additional feature, circumferential slots 104 provide a pathwaythrough which vessel side branches can be accessed for catheterinterventions. Should stent segment 32 be deployed at a location inwhich it covers the ostium of a side branch to which access is desired,a balloon dilatation catheter may be positioned through circumferentialslot 104 and expanded. This deforms circumferential struts 109, 111axially outward, thereby expanding circumferential slot 104 and furtherexpanding upper and lower slots 102, as shown in phantom in FIG. 3B.This provides a relatively large opening 120 through which a cathetermay be inserted through stent segment 32 and into the side branch forplacing stents, performing angioplasty, or carrying out otherinterventions.

FIGS. 6A-6B illustrate a second embodiment of a stent segment 32according to the invention. In FIG. 6A, a portion of stent segment 32 isshown in a planar shape for clarity. Similar to the embodiment of FIG.5A, stent segment 32 comprises two parallel rows 122A, 122B of I-shapedcells 124 formed into a cylindrical shape around axial axis A. Cells 124have upper and lower axial slots 126 and a connecting circumferentialslot 128. Upper and lower slots 126 are bounded by upper axial struts130, lower axial struts 132, curved outer ends 134, and curved innerends 136. Circumferential slots 128 are bounded by outer circumferentialstrut 138 and inner circumferential strut 140. Each I-shaped cell 124 isconnected to the adjacent I-shaped cell 124 in the same row 122 by acircumferential connecting strut 142. Row 122A is connected to row 122Bby the merger or joining of curved inner ends 136 of at least one ofupper and lower slots 126 in each cell 124.

One of the differences between the embodiment of FIGS. 6A-6B and that ofFIGS. 5A-5B is the way in which spacing is maintained between adjacentstent segments. In place of the spacing members 112 of the earlierembodiment, the embodiment of FIG. 6A includes a bulge 144 in upper andlower axial struts 130, 132 extending circumferentially outwardly fromaxial slots 126. These give axial slots 126 an arrowhead or cross shapeat their inner and outer ends. The bulge 144 in each upper axial strut130 extends toward the bulge 144 in a lower axial strut 132 in the samecell 100 or in an adjacent cell 100, thus creating a concave abutment146 in the space between each axial slot 126. Concave abutments 146 areconfigured to receive and engage curved outer ends 134 of cells 124 inthe adjacent stent segment, thereby maintaining spacing between thestent segments. The axial location of bulges 144 along upper and loweraxial struts 130, 132 may be selected to provide the desired degree ofinter-segment spacing.

FIG. 6B shows two stent segments 32 of FIG. 6A in an expanded condition.It may be seen that axial slots 124 are deformed into acircumferentially widened modified diamond shape with bulges 144 on thenow diagonal upper and lower axial struts 130, 132. Circumferentialslots 128 are generally the same size and shape as in the unexpandedconfiguration. Bulges 144 have been pulled away from each other to someextent, but still provide a concave abutment 146 to maintain a minimumdegree of spacing between adjacent stent segments. As in the earlierembodiment, some axial shortening of each segment occurs upon expansionand stent geometry can be optimized to provide the ideal intersegmentspacing.

It should also be noted that the embodiment of FIGS. 6A-6B retains thefeature described above with respect to FIGS. 5A-5B to enable access tovessel side branches blocked by stent segment 32. Should such sidebranch access be desired, a dilatation catheter may be inserted intocircumferential slot 128 and expanded to provide an enlarged openingthrough which a side branch may be entered. Other preferred geometriesfor stent segments 32 are described in U.S. patent application Ser. No.10/738,666 (Attorney Docket No. 021629-000510US), with is hereby fullyincorporated by reference.

Referring now to FIGS. 7A-7E, the use of the stent delivery catheter ofthe invention will be described. While the invention will be describedin the context of coronary artery treatment, the invention is useful inany of a variety of blood vessels and other body lumens in which stentsare deployed, including the carotid, femoral, iliac and other arteries,as well as veins and other fluid-carrying vessels. A guiding catheter(not shown) is first inserted into a peripheral artery such as thefemoral and advanced to the ostium of the target coronary artery. Aguidewire GW is then inserted through the guiding catheter into thecoronary artery A where lesion L is to be treated. The proximal end ofguidewire GW is then inserted through nosecone 28 and guidewire tube 34outside the patient's body and stent delivery catheter 20 is slidablyadvanced over guidewire GW and through the guiding catheter into thecoronary artery A. Stent delivery catheter 20 is positioned through alesion L to be treated such that nosecone 28 is distal to lesion L.During this positioning, sheath 25 is positioned distally up to nosecone28 so as to surround expandable member 24 and all of the stent segments32 thereon.

Optionally, lesion L may be predilated prior to stent deployment.Predilatation may be performed prior to introduction of stent deliverycatheter 20 by inserting an angioplasty catheter over guidewire GW anddilating lesion L. Alternatively, stent delivery catheter 20 may be usedfor predilitation by retracting sheath 25 along with stent segments 32to expose an extremity of expandable member 24 long enough to extendthrough the entire lesion. This may be done while delivery catheter 20is positioned proximally of lesion L or with expandable member 24extending through lesion L. Fluoroscopy enables the user to visualizethe extent of sheath retraction relative to lesion L by observing theposition of marker 56 on sheath 25 relative to marker 82 at the distalend of expandable member 24. To allow stent segments 32 to moveproximally relative to expandable member 24, force is released frompusher tube 86 and valve member 58 engages and draws the stent segmentsproximally with sheath 25. With the appropriate length of expandablemember 24 exposed, expandable member 24 is positioned within lesion Land inflation fluid is introduced through inflation lumen 66 to inflateexpandable member 24 distally of sheath 25 and thereby dilate lesion L.Expandable member 24 is then deflated and retracted within sheath 25while maintaining force on pusher tube 86 so that stent segments 32 arepositioned up to the distal end of expandable member 24, surrounded bysheath 25. Alternative embodiments of devices and methods for lesionpredilatation are described in detail below.

Following any predilatation, stent delivery catheter 20 is repositionedin artery A so that nosecone 28 is distal to lesion L as shown in FIG.7A. Sheath 25 is then retracted as in FIG. 7B to expose the appropriatenumber of stent segments 32 to cover lesion L. Again, fluoroscopy can beused to visualize the position of sheath 25 by observing marker 56thereon relative to marker 82 within expandable member 24. As sheath 25is drawn proximally, force is maintained against pusher tube 86 so thatstent segments 32 remain positioned up to the distal end of expandablemember 24. It should also be noted that sheath 25 moves proximallyrelative to guidewire tube 34, which slides through guidewire tube exitport 35. Advantageously, regardless of the position of sheath 25,guidewire tube 34 provides a smooth and continuous passage for guidewireGW so that stent delivery catheter slides easily over guidewire GW.Optionally, a distal portion of expandable member 24 may have adifferent size of may be made of a different material or differentpolymeric formulation than the remainder of expandable member 24 so asto be more suited for pre- or post-dilatation. For example, the distalportion of expandable member 24 may be less compliant than the remainderof the expandable member and/or may be made of a more hard or durablepolymer suited to higher-pressure inflation for displacement of stenoticmaterial.

With the desired number of stent segments 32 exposed distally of sheath25, it is frequently desirable to create some spacing between the stentsegments to be deployed and those remaining enclosed within sheath 25.This reduces the risk of dislodging or partially expanding thedistal-most stent segment 32 within sheath 25 when expandable member 24is inflated. Such spacing is created, as shown in FIG. 7C, by releasingforce against pusher tube 86 and retracting sheath 25 further proximallya short distance. The engagement of valve member 58 with stent segments32 moves those stent segments 32 within sheath 25 away from those stentsegments 32 distal to sheath 25. The length of this spacing ispreferably equal to the length of about ½-1 stent segment.

Expandable member 24 is then inflated by delivering inflation fluidthrough inflation lumen 66, as shown in FIG. 7D. The exposed distalportion of expandable member 24 expands so as to expand stent segments32 thereon into engagement with lesion L. If predilatation was notperformed, lesion L may be dilated during the deployment of stentsegments 32 by appropriate expansion of expandable member 24. Sheath 25constrains the expansion of the proximal portion of expandable member 24and those stent segments 32 within sheath 25.

Expandable member 24 is then deflated, leaving stent segments 32 in aplastically-deformed, expanded configuration within lesion L, as shownin FIG. 7E. The alternative embodiment of stent segment 32 illustratedin FIGS. 6A-6B is shown in a similarly expanded condition in FIG. 8.With stent segments 32 deployed, expandable member 24 may be retractedwithin sheath 25, again maintaining force against pusher tube 86 toposition stent segments 32 at the distal end of expandable member 24.Expandable member 24 is moved proximally relative to stent segments 32until the distal-most stent segment engages stop 78 (FIGS. 2A-2B),thereby placing stent segments 32 in position for deployment. Stentdelivery catheter 20 is then ready to be repositioned at a differentlesion in the same or different artery, and additional stent segmentsmay be deployed. During such repositioning, guidewire tube 34facilitates smooth tracking over guidewire GW. Advantageously, multiplelesions of various lengths may be treated in this way without removingstent delivery catheter 20 from the patient's body. Should there be aneed to exchange stent delivery catheter 20 with other catheters to beintroduced over guidewire GW, guidewire tube 34 facilitates quick andeasy exchanges.

When the movement of the pusher tube, sheath, or stent segments isdescribed in relation to other components of the delivery catheter ofthe invention, such movement is relative and will encompass both movingthe sheath, pusher tube, or stent segments while keeping the othercomponent(s) stationary, keeping the sheath, pusher tube or stentsegments stationary while moving the other component(s), or movingmultiple components simultaneously relative to each other.

Referring now to FIG. 9, one embodiment of a stent delivery catheterdevice 150 suitably includes a stent expansion member 152 over which astent having multiple stent segments 154 may be positioned, an innersheath 156 disposed over stent segments 154 and stent expansion member152, a pusher member 158 for slidably advancing stent segments 154 alongexpansion member 152, a nosecone 164, and a dilatation member 160coupled with an outer sheath 162. Inner sheath may include a stentseparation member 157 for separating adjacent stent segments 154. Outersheath 162 may be disposed over inner sheath 156 to form an inflationlumen 163 for expanding dilation member 160. Alternatively, theinflation lumen may be disposed within the wall of inner sheath 156, orit may comprise a tube or lumen fixed or molded on the exterior wall ofinner sheath 156. As with other embodiments previously described,catheter device 150 may be delivered over a guidewire 166.

Stent delivery catheter device 150 could be used similarly to many ofthe embodiments described above, with the additional feature of usingdilatation member 160 to pre-dilate a lesion before placing one or morestent segments 154 at the lesion. Additionally, after pre-dilatation andstent segment placement, dilatation member 160 may also be positioned,in its deflated form, within one or more expanded stent segments 154 andexpanded to further expand stent segments 154, to confirm completeexpansion of stent segments 154, to further dilate the lesion and/or thelike. Outer sheath 162 and inner sheath 156 are typically retractabletogether to expose one or more stent segments 154 and/or a portion ofstent expansion member 152. Stent separation member 157 may be used toseparate adjacent stent segments 154, to retract slidable stent segments154 over stent expansion member 152, and/or to hold stent segments 154in place while stent expansion member 152 is advanced. In the embodimentshown in FIG. 9, stent segments 154 may alternatively be self-expanding,wherein inner sheath 156 restrains stent segments 154 from expansionuntil it is retracted to allow one or more of the stent segments toself-expand into the lesion at the treatment site.

Referring now to FIG. 10, another embodiment of a stent deliverycatheter device 170 may include a stent expansion member 172, a stenthaving stent segments 174 positionable on stent expansion member 172, asheath 176 disposed over expandable member 172 and stent segments 174and having a stent separation member 177, a pusher member 178, anosecone 184, a slidable inner shaft 192, and a dilatation member 190disposed along slidable inner shaft 192. Again, catheter device 170 maybe advanced along a guidewire 186. In alternative embodiments,low-profile, flexible shaft may be fixed to and extend distally fromnosecone 184, rather than being slidable, with dilatation member 190coupled to its distal end. Alternatively, a dilatation member may becoupled with the nosecone itself, and/or the like.

Slidable inner shaft 192 may be moved axially in distal and proximaldirections (two-headed arrow) to expose all or a portion of dilatationmember 190 and to retract all or a portion back into nosecone 184 and/orfirst expandable member 172. In an alternative embodiment, dilatationmember 190 may be significantly longer than the one shown in FIG. 10(for example, about 30-100 mm), such that only a portion of dilatationmember 190 is typically advanced out of the distal end of nosecone 184.This allows the user to adjust the length of the expanded portion ofsecond expandable member 190 so as to match the length of the lesionbeing dilated. Nosecone 184 restrains the unexposed portion of secondexpandable member 190 from expansion while the exposed distal portion isexpanded. In any case, dilatation member 190 may be used to pre-dilate alesion before placing stent segments 174 and may also be used to furtherexpand the placed segments 174, further expand a lesion after placementof segments 174 and/or the like.

FIGS. 11A and 11B demonstrate a method for dilating a lesion L in avessel V and placing stent segments according to one embodiment. In thisembodiment, a stent delivery catheter device 200 is positioned in avessel V in a location for treating a lesion L, for example by passingdevice 200 over a guidewire 216 or by any other suitable positioningmethod. A sheath 206 may then be retracted and/or an expandable member202 may be advanced to expose a portion of expandable member 202distally of sheath 206. As sheath 206 is retracted, a stentseparation/retaining member 207 may slide stent segments 204 proximallyrelative to expandable member 202 to expose a desired length ofexpandable member 202 coextensive with lesion L. The exposed portion ofexpandable member 202, without stent segments 202 thereon, may then beexpanded (solid-tipped arrows) to pre-dilate the lesion. Expandablemember 202 may then be deflated/unexpanded and retracted back into aposition within stent segments 204. Alternatively or additionally,sheath 206 and pusher 208 may be used to slidably advance stent segments204 over the now-unexpanded expandable member 202.

As shown in FIG. 11B, sheath 206 may next be retracted to expose bothstent segments 204 and expandable member 202. The number of stentsegments 204 and the length of expandable member 202 are selected tomatch the length of the lesion L. In some embodiments, stent segments204 self-expand to contact the lesion L, while in other embodiments,stent segments 204 are expanded by expandable member 202. Once stentsegments 204 are expanded, expandable member 202 may optionally bere-expanded to further expand segments 204, assure that segments 204 arefully expanded, further expand lesion L or the like. In someembodiments, further lesions along the vessel V may be additionallytreated by repositioning device 200, pre-dilating the additionallesion(s), placing stent segments, and the like.

FIGS. 12A-12E show another embodiment of a method for dilating andplacing a stent in a lesion L. A stent delivery catheter device 220 isadvanced over a guidewire 236 to a position in a vessel V for treatingthe lesion L. In one embodiment, catheter device 220 includes an outersheath 232 coupled with an outer expandable member 230, both of whichare slidably disposed over an inner catheter body 221. As shown in FIG.12B, outer expandable member 230 may then be expanded to contact andexpand the portion of the vessel V containing the lesion. Outerexpandable member 230 may then be deflated and retracted, along withouter sheath 232, as shown in FIG. 12C. Retracting outer sheath 232 andouter expandable member 230 may expose a stent having one or more stentsegments 224 as well as an inner expandable member 222. In oneembodiment, as shown in FIG. 12D, stent segments 224 may self-expand tocontact the lesion. As shown in FIG. 12E an additional optional step mayinclude expanding inner expandable member 222 to further dilate thelesion L, further expand segments 224, assure expansion of segments 224and/or the like.

A number of additions, variations and modifications of the method justdescribed may be made in various embodiments. For example, in analternative embodiment, outer expandable member 230 may be moveddistally after expansion of segments 224 and may be re-expanded tofurther expand segments. In such an embodiment, it may be necessary tohave only one expandable member, such as outer expandable member 230. Inother embodiments, such as described in relation to FIGS. 11A and 11B,only an inner expandable member is used. Also, in various embodimentsany suitable combination and order of dilation and stent placement stepsmay be employed. Furthermore, various embodiments of the devices andmethods described above for dilatation in combination with stentplacement may be used with any of a variety of stents and stent deliverysystems, including those described in U.S. patent application Ser. Nos.10/306,622 (Attorney Docket No. 021629-00010US) and 10/306,620 (AttorneyDocket No. 021629-000210US), both of which were filed on Nov. 27, 2002,and both of which are hereby fully incorporated by reference.

Therefore, although the above is complete description of the preferredembodiments of the invention, various alternatives, additions,modifications and improvements may be made without departing from thescope thereof. For example, while the foregoing description of theinvention is directed to a stent delivery catheter for deploying stentsinto vascular lumens to maintain patency, various other types ofwire-guided catheters also may embody the principles of the invention.For example, balloon catheters for angioplasty and other purposes,particularly those having a slidable external sheath surrounding theballoon, may be constructed in accordance with the invention. Othertypes of catheters for deployment of prosthetic devices such as emboliccoils, stent grafts, aneurism repair devices, annuloplasty rings, heartvalves, anastomosis devices, staples or clips, as well as ultrasound andangiography catheters, electrophysiological mapping and ablationcatheters, and other devices may also utilize the principles of theinvention. Thus, the above description is provided primarily forexemplary purposes and should not be interpreted to limit the scope ofthe claims as they are set forth below.

1. A stent delivery device for delivering at least one stent to a treatment site, the device comprising: a catheter shaft having a proximal end and a distal end; an expandable member coupled with the catheter shaft near the distal end; at least one stent slidably positionable on the expandable member; and at least one axially movable sheath disposed over at least part of the expandable member and stent thereon, wherein the sheath is axially movable relative to the catheter body to expose at least a portion of the expandable member without exposing the stent, and wherein the sheath is also movable to expose at least a portion of the stent to allow it to expand.
 2. A device as in claim 1, wherein the exposed portion of the expandable member is expanded to dilate a lesion at the treatment site, and wherein a length of the exposed portion of is selected in situ.
 3. A device as in claim 1, wherein a length of the exposed portion of the stent is selected in situ.
 4. A device as in claim 1, wherein the stent is self-expanding.
 5. A device as in claim 1, further including a pusher member for advancing the stent along the expandable member.
 6. A device as in claim 1, wherein the stent comprises a plurality of separable, self-expanding stent segments.
 7. A device as in claim 6, wherein the sheath is configured to constrain expansion of a first plurality of the stent segments while allowing expansion of a second plurality of the stent segments.
 8. A device as in claim 7, wherein the sheath further comprises at least one separation device for separating the first plurality of stent segments from the second plurality, thus allowing for expansion of a stent segment without interfering with adjacent stent segments.
 9. A device as in claim 6, wherein the stent segments comprise a thermal shape memory material, and wherein the expandable member is configured to accept one or more heated or cooled fluids to change a temperature of the stent segments.
 10. A stent delivery device for treating a target site in a vessel, the device comprising: a catheter shaft having a proximal end and a distal end; a first stent carried on the catheter shaft and being deployable therefrom; a second stent carried on the catheter shaft and being deployable therefrom independently of the first stent; and a dilatation member for dilating the target site independently of deploying the first and second stents.
 11. A stent delivery device for delivering at least one stent to a treatment site, the device comprising: a catheter shaft having a proximal end and a distal end; a stent expansion member coupled with the catheter shaft near the distal end; at least one stent positionable on the stent expansion member; at least one axially movable sheath disposed over at least part of the stent expansion member and stent thereon; and a dilatation member coupled with the sheath for dilating one or more lesions at the treatment site.
 12. A device as in claim 11, wherein the stent comprises a plurality of separable stent segments.
 13. A device as in claim 12, wherein the separable stent segments are axially movable along the stent expansion member.
 14. A device as in claim 13, further comprising a pusher member for advancing the stent segments axially along the stent expansion member.
 15. A device as in claim 12, wherein the sheath is configured to constrain expansion of a first portion of the stent expansion member and a first plurality of the stent segments while allowing expansion of a second portion of the stent expansion member and a second plurality of the stent segments.
 16. A device as in claim 15, wherein the sheath further comprises at least one separation device for separating the first plurality of stent segments from the second plurality, thus allowing for expansion of a stent segment by the stent expansion member without interfering with adjacent stent segments.
 17. A device as in claim 11, wherein the stent expansion member and the dilatation member are independently expandable.
 18. A device as in claim 17, further including at least one inflation lumen for expanding the dilatation member.
 19. A device as in claim 18, wherein the inflation lumen comprises a tubular member disposed concentrically over the sheath.
 20. A device as in claim 18, wherein the inflation lumen comprises a tubular member coupled with and extending along the outer surface of the sheath.
 21. A device as in claim 18, wherein the inflation lumen is disposed within a wall of the sheath.
 22. A method for delivering at least one stent to a treatment site, the method comprising: positioning a distal portion of a stent delivery catheter device at the treatment site, the stent delivery catheter carrying at least one stent; expanding at least a portion of an expandable member on the catheter device to dilate at least a portion of a lesion at the treatment site; selecting a deployable portion of the stent having a selected length; and expanding the deployable portion of the stent at the treatment site, an undeployed portion of the stent remaining in the delivery catheter.
 23. A method as in claim 22, further comprising positioning the deployable portion of the stent over the expandable member.
 24. A method as in claim 22, wherein expanding the deployable portion of the stent comprises expanding the expandable member.
 25. A method as in claim 22, further comprising retracting a sheath disposed over the expandable member to expose at least the portion of the expandable member before dilating the lesion.
 26. A method as in claim 25, wherein retracting the sheath also retracts the at least one stent relative to the expandable member.
 27. A method as in claim 22, wherein the at least one stent comprises a plurality of stent segments, and wherein positioning at least the portion of the at least one stent over the expandable member comprises positioning at least one stent segment over the expandable member.
 28. A method as in claim 27, wherein positioning the at least one stent segment over the expandable member comprises: allowing the expandable member to return to an unexpanded form; and retracting the unexpanded expandable member to a position within the at least one stent segment.
 29. A method as in claim 28, further comprising retracting a sheath disposed over the expandable member and the plurality of stent segments to expose at least the portion of the expandable member and stent segments thereon.
 30. A method for delivering at least one stent segment to a treatment site, the method comprising: positioning a distal portion of a stent delivery catheter device at the treatment site, the stent delivery catheter carrying at least one stent; expanding at least a portion of an expandable member on the catheter device to dilate at least a portion of a lesion at the treatment site; and retracting a sheath on the catheter device to expose at least a portion of the at least one stent from within the sheath, the portion self-expanding at the treatment site.
 31. A method as in claim 30, wherein the at least one stent comprises a plurality of stent segments, and wherein retracting the sheath exposes at least one of the stent segments to self-expand at the treatment site.
 32. A method as in claim 31, further comprising, after retracting the sheath: positioning the expandable member within the at least one self-expanded stent segment; and expanding at least a portion of the expandable member to further expand the stent segment.
 33. A method as in claim 30, further comprising exposing the portion of the expandable member outside the sheath before the expanding step.
 34. A method as in claim 33, further comprising retracting the portion of the expandable member to a position within the sheath after the expanding step.
 35. A method as in claim 30, further comprising passing a fluid through the expandable member while the stent segments are disposed thereon, wherein the stent segments comprise a thermal shape memory material, and wherein passing the fluid changes the temperature of the stent segments.
 36. A method as in claim 35, wherein the passed fluid is heated to a temperature higher than body temperature.
 37. A method as in claim 35, wherein the passed fluid is cooled to a temperature lower than body temperature.
 38. A method as in claim 35, wherein the portion of the expandable member is expanded using the fluid. 